The present invention relates to an information recording disc implemented as a disc type recording medium and, more particularly, to an information recording disc adapted to handle efficiently both large amounts of previously recorded data and additional information recorded thereon by a user.
One representative type of conventional optical disc is a CD-ROM (compact disc read only memory), which is a disc type recording medium. This type of disc is manufactured as follows: While an original disc is being cut, data signals are recorded thereon by use of a pit pattern of tiny bumps and dents. When finished, the original disc is copied so as to produce at low cost large quantities of optical discs containing the same data.
Recent developments in this field include writable optical discs whose contents may be deleted or overwritten with new data.
Where optical discs are used as the medium for providing users with programs or data, it takes too much time and cost to record the data on each disc one at a time for the individual users. Meanwhile, it is not a good practice of maintaining software resources if the user is to use and handle two discs separately: one being an optical disc cut from the original disc and containing the prerecorded program and/or data, and the other an optical disc on which the user records his own information.
One solution to the above dual disc disadvantage is proposed in Japanese Patent Laid-Open No. 62-173630. The disclosure envisages one optical disc comprising both read-only prerecorded data areas and data write areas, the latter being the domain in which the user may write his own data.
On the above optical disc, data is prerecorded on the read-only areas using the pit pattern of tiny bumps and dents when the disc is cut from its original. This prior art method of recording data makes it easier to copy optical discs containing data. The method also allows the user to record his own data onto the data write areas on the disc. Thus the time and the cost required for manufacture of the optical discs are reduced, and the discs produced in this manner are easy to maintain.
The above-described conventional optical disc has inner and outer concentric band type areas on the surface thereof. The inner areas are the read-only prerecorded data areas (ROM), and the outer areas are the data write areas (RAM) to which data may be added later. When writing and reading data to and from this optical disc, the system must use the predetermined read-only and data write areas. Thus, it is difficult to use one optical disc for different purposes depending on application programs. Further, where an application program handles large amounts of data, it is important to improve the throughput or the optical disc system. With the prior art disc, however, it takes time to move the pickup over the surface thereof for access to data.